1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a program. More particularly, the present invention relates to an image processing apparatus, an image processing method, and a program that perform a process for generating a motion compensated image and reducing noise in images.
2. Description of the Related Art
Images captured using, for example, cameras, video imaging devices, or the like contain a not insignificant amount of noise. Often, much noise is contained in captured images in, in particular, image capturing at a low illumination or in a short exposure time period. One of the causes for this is that in a case where image capturing at a low illumination or for a short exposure time period is performed, the amount of incident light is small and the amount of stored charge of image-capturing elements is decreased. In order to obtain a bright image on the basis of such image-captured data, amplification of a signal becomes necessary. During this amplification process, noise that occurs in image-capturing elements and/or analog circuits is amplified, and a resulting image is an image having much noise.
In order to decrease noise, exposure for a long time period is effective, but if exposure for a long time period is performed, there is a possibility that blurring of an image due to camera shake during exposure occurs. Another method is available in which continuous image capturing is performed in which image capturing is repeated at a high shutter speed at which exposure blurring hardly occurs, and a plurality of images obtained by the continuous image capturing are addition-averaged, thereby reducing noise that is not correlated with respect to the time direction. However, this process for adding a plurality of images takes many calculations, thereby decreasing processing efficiency.
Techniques for reducing noise of an image according to examples of the related art are, for example, disclosed in the following documents.
Japanese Unexamined Patent Application Publication No. 9-261526 discloses a configuration in which camera shake of a plurality of images obtained by continuous image capturing is corrected, and these images are superposed.
Japanese Unexamined Patent Application Publication No. 11-75105 discloses a configuration in which the total exposure time period is divided into a plurality of exposure periods, and images obtained in respective exposure periods are subjected to shake correction and added together, thereby realizing improvement in the image quality.
In both the configurations disclosed in Japanese Unexamined Patent Application Publication Nos. 9-261526 and 11-75105, a motion vector is detected from a plurality of images so as to obtain motion information among a plurality of images, and images are combined by using the motion information. However, as described above, a process for adding images takes many calculations, and thus the processing efficiency is decreased.